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Re: anyone a Madagascar expert?



you wrote:
> I guess this is my week to ask for help.
> We have a display of small Triassic fossils from Madagascar . We were
> supposed to have received background info on these two years ago, but
> nothing has ever arrived, and there are no records of who the individual
> was that was supposed to provide such data.
> Does anyone know someone who might be able to give us a little more
> information about Madagascar during Triassic, the significance (or even
> lack of it) of these fossils or at least a few sentences that we can
> explain SOMETHING about them or about the significance of Madagascar? If
> you know a good reference work that covers these (that a layman would
> understand) or where we might be able to see such a work, I'd appreciate
> some help. Just point me in the right direction!
> Here's the list:
> Boreosomus sp.
> Ecrinosomus dixoni
> Perleideus madagascariensis
> Pteronisculus sp.
> Australosomus merlei
> Saurichthys sp.
> Tangasaurus benelli
> Bobosatrania groenlandica

(First of all, I am definitely NOT a Madagascar expert)

As far as I know, the fossils you mention represent primitive
actinopterygians that are known from early Triassic ('Eotrias' in the
older literature) lacustrine sediments of Madagascar. These fishes
have been studied and described by the French paleontologists
Lehman and Piveteau, together with a variety of temnospondyls
(Mahavisaurus, Ifasaurus, Wantzosaurus,...).
Tangasaurus is a presumably aquatic diapsid that is known from late
Permian beds of Madagascar and Tanzania. Late Permian strata of
Madagascar have yielded a very peculiar fauna mainly consisting of
specialized diapsids (Coelurosauravus, Thadeosaurus, Hovasaurus,
Tangasaurus, Claudiosaurus), very different from the therapsid
dominated fauna of the contemporaneous Karoo beds of Southern Africa.
The aquatic diapsids have been studied mainly by Robert Carroll and
Phil Currie. Recently, a new tetrapod assemblage has been discovered
of probably Late Triassic  Late Triassic age, with a rhynchosaur
(Isalorhynchus) and a gomphodont cynodont (yet to be named and
described, but apparently similar to Exaeretodon of South America and
India) (see an abstact of the latest SVP congress, i.a. by Parrish,
does anyone on this list (who has been there) know more of it?).
Madagascar was part of the large Gondwana supercontinent during
Permian and Triassic times, squeezed between Africa, India, Australia
and Antarctica.

The fish have been described in hard to find and rather obscure
publications (from France and Norway) e.g.

Piveteau 1935: Paléontologie de Madagascar XXI. Les poissons du Trias
inférieur. Contribution à l'étude des Actinoptérygiens. Ann. Pal. 23,
81-180.
Lehman 1952: Etude complementaire des poissons de l'Eotrias de
Madagascar. K. Svenska Vetenskapsakad. Handl 2 ser 6, no 6.

For some more information on the diapsids, see

Carroll 1981. Plesiosaur ancestors from the Upper Permian of
Madagascar. Philos. Trans. R. Soc. London Ser B. 293, p 315-383.
Currie 1982. The anatomy and relationships of Tangasaurus mennelli
Haughton (Reptilia, Eosuchia). Ann. S. Afr. Mus. 86, p247-256.

Pieter Depuydt